Carbon vs Fibre - when is it faster or slower?

Hi,

I wanted to start a discussion on this subject. Is the carbon faster than a fibre glass and when? Or are there times when fibre is actually preferable to carbon?

Fibre has a bit of flex. When on the runs the back of the boat is lifted causing the hull to flex and this gives the boat a 'natural' rocker. So with this 'makeshift' rocker, does a fibre actually stay on the runs longer and better? Does that added momentum keep on the boat on the runs longer?

Weight aside, the carbon is a much stiffer boat. When does this come into play to make a difference to speed (if at all)? On the flip side, does the flex in fibre loose energy or is this so marginal not to make a difference.

Does the weight difference of 4 kg really make a difference when you're pushing this across a horizontal?

Whilst the lighter weight alone of Carbon Fibre (CF) can aid boat-speed in many conditions over Glass, a major benefit is it's stiffness - the ski is stiffer and is more responsive to inputs (paddler's stroke).

So there may be less engery loss, or better energy transfer, using a stiffer (more responsive?) hull.

Then I think there is a theory that, if you were to save, say 4kg's in weight on ANY ski (which is often the actual difference between CF and GF ski's), would it be better to be a 4-kg lighter paddler, or on a 4 kg lighter ski?!

I'll let the experts handle that one!

But to illustrate using a different sport, in cycling, there are 3 'types' of weight; the weight of the RIDER, the weight of the BICYCLE and the weight of the ROTATIONAL parts (wheels and pedals and cranks, primarily).

The theory exists that ROTATIONAL weight carries a higher 'penalty' than FIXED weight (either rider or non-rotational parts). Weight is weight, but rotational weight carries a higher corresponding penalty!

So if Joe Average has a, say 16kg ski, would he be better with a 12kg ski or losing 4 kg's in weight....?

I only know which one would be CHEAPER!

I'm going to hazard a guess that on a good / proven design, e.g. Fenn Elite, a Carbon will always be faster in clean conditions e.g. no chop. I raced in my glass Elite yesterday, which I think clocks in at 17kgs, and cannot see how I would not have been a few hundred meters ahead with say 5kgs less in tow. Regardless of performance benefits, which I'm sure are there, and with I-can-carry-the-weight hardmanness aside, I'm tired of lugging around my heavy ski, and will most likely buy a primary racing carbon in the next few months. The question is just which ski, despite Fenn always been a surefire choice.

Here's my study design to answer your questions.

1 Paddler
1 Paddle
2 Skis that look identical, e.g. with coloured gel, and made from the same mold (Boat A - carbon @ 12 kg and Boat B - fg at 16 kg)
1 GPS system.
1 Friend to carry the ski to the water

Select a 10 km course in a bay or ocean. Paddle exactly the same course every Tuesday and Thursday at the same time, e.g. 12 noon. Have a computer randomly assign boat A or B to either the Tuesday or Thursday each week. Have a friend carry the ski to the water and place it in the water so that the paddler doesn't physically lift the weight of the ski.

Paddle at 80% of maximum effort.

Record each session on a GPS and also record wind strength, wind direction, wave height, paddler heart rate and paddler weight.

Repeat this every week for 2 years so that you have approx 100 time trials in each boat with average speed for each run.

Compare the average speed over 100 time trials for boat A and boat B.

I think by doing this you could almost eliminate the variables. Ideally, the wind strength, wind direction, wave height, paddler heart rate and paddler weight for each of the 100 time trials for boat A verses boat B would be analysed to ensure that there were no statistically significant differences in these variables. Hopefully, the conditions for boats A and B are shown to be similar over the two year period otherwise it's going to be difficult to compare the results.

Also, it would be preferable to have more than one paddler (perhaps paddlers with difference weights, abilities and difference sexes) complete the same two year trial so that the results can be pooled.

If carbon is shown to be faster than fg overall, you could then take a subset of the results recorded at different wave heights for both boat A and boat B. Perhaps flat conditions and > 1m. By comparing these results it may (but I suspect not) help determine whether the "flex" in the waves makes a difference. It there is a greater time advantage for carbon in the flat verses in waves compared to fg it could mean that the flex of fg boats is beneficial for catching runs.

or you could look at Wesley's chart, cos that pretty much sums up his criteria.

I had an old glass V10 which weighed 17.5kg and trained in it nearly everyday for a year in a relatively protected waterway with chop, and in the ocean. I also did a couple of 20km down-winds in biggish conditions.

I have since purchased a 14kg SA-manufactured carbon V10. Not much weight difference, though it feels significant under the arm.

My immediate impression was that the new boat was twitchier, reacting to every little chop and wave. It was also more predictable, though my reflexes had to be quicker. The BIG difference was in picking up runners. It was SO MUCH more responsive, and took much less effort to pick them up, even small chop. Staying on waves was also easier - it was more recoverable from broaches, and held a tighter line across waves. Upwind it tends to be more reactive, and psychologically quicker, though I suspect that there is little speed difference.

The different behaviour relates to STIFFNESS and the ability of the hull to retain its (intended) shape. THAT is the important bit. Whilst It feels 'lighter' in the water, the weight difference is too small to be significant.

Newton's Second law of motion states that F=ma2. So an extra 4kg of boat weight in a total body+boat weight of 80kg, requires only a 5% difference in force to accelerate it at the same rate. This is not really significant. However, over a race distance it would be, as one is constantly accelerating, especially in choppy or downwind conditions.

However, (and this is the big BUT), one would be quicker with a lighter boat than a lighter body because one is dynamic weight (boat) and the other (body) is relatively static.

Whether one is designing race cars where one tries to get the weight out of the wheels (alloy), tyres (low profile), and suspension (alloy); or yachts/boats/skis/kayaks where one concentrates on getting the weight down and out of the ends and mast (to reduce the hobby-horse effect); the important factor for performance tends to be stiffness more so than weight.

These observations are reflected in Rob's article 'Stiffness and Stability'.

And the bottom line? As Oscar frequently states: 'The fastest boat is the boat that you are fastest in.' If you are a beginner, go for glass. If you are not at the elite end of the field, take a cheaper and (normally) more durable option.

Hi there,

Thanks for all the opinions and feedback. There does not seem to be too much controversy here (yet) - everyone seems to be on the same message. I thought there would be some voices arguing for the glass on the runs but the feedback seems to be that is actually helps to get onto the runs. I paddled my Red 70 pro which is weighing in at 18 and a bit kg this morning and it felt heavy, but so were my eyelids so that might have been more the reason. I'm 75 kg so looking forward to getting onto a 11 kg EOS to feel the difference.

Keep the feedback coming.

Oxbow wrote:

I have since purchased a 14kg SA-manufactured carbon V10.

Wow, that's heavy compared to the 9.5kg Elite Carbon export (china) boats.

Are they purposely built heavier for durability in SA?

I heard a rumor to that effect, but judging by the amount of repairs using paint rather than gelcoat (I suspect triping issues), it could have been an apprentice.

It is always a compromise. Greg Barton, in his Surfski Info interview re the V8 indicated that Epic were slightly increasing the weight in their skis to provide greater durability.

It is important to note that strength can be assessed many ways and stiffness does not necessarily equate to strength, and vice-versa. i.e. a super stiff carbon lay-up is susceptible to punctures as there is no 'give' and all of the force is applied instantaneously to a small point. In contrast a soft plastic boat will grind over rocks all day, but may be compromised in performance due to lack of stiffness or weight, or both.

And if you do damage a craft made from exotic materials (carbon / kevlar), the repair cost will be much greater than for a glass boat.

How many of the Top 10 paddlers are on the fiber versus Carbon? I would imagine most if not all are then carbon based (life forms).

How many of the Top 10 paddlers are on the fiber versus Carbon?

I can't imagine any of them would be paddling a glass ski out of choice!

I'm not saying these are the top ten, but they are all elite paddlers...

Mocke: Carbon Fenn
Matt Bouman: Carbon Epic
Oscar Chalupsky: Carbon Epic
Herman Chalupsky: Carbon Epic
Hank McGregor: Carbon Epic
Sean Rice: Carbon Think
Tom Schilperoort: just showed his preference for a carbon ski. Has a carbon Epic on the way.
Tim Jacobs: Carbon Nelo
Jeremy Cotter: Carbon Fenn
Dean Gardiner: Carbon Fenn
Murray Stewart: Carbon Fenn
Tony Schumacher: Carbon Epic
Ben Allen: Carbon Think
Ken Wallace: Carbon Think

Thanks Rob. I had a look at the article where you were comparing the cork Green to Carbon Red 70 pro. Seems you were looking towards the stability issue. Are you going to extend it further to speed on the runs and speed on the flat?

The key to a craft's performance is the stiffness - carbon and core layups give you this (normal glass and a Core can also achieve this). I would rather paddle a stiff ski of 15kg than soft 10 kg ski.

The less the flex the more unstable the ski will be as the ski will not 'bend' to the water shape or increase rocker with the paddler's weight.

Are you going to extend it further to speed on the runs and speed on the flat?

We don't have access to those boats anymore - it was just a once-off opportunity where we had a stiff carbon boat and a flexible cork composite boat that were identical in weight...

The stability was the overwhelming factor in the choppy water - the stiffness was a disadvantage to us in those conditions and the flexible boat was faster because we were able to paddle it properly; the stiff boat was very difficult to handle!

I have had two Green7s: the first one was lighter and more flexible - but eventually delaminated. It was the first pre-production ski and for all the following boats they added material around the cockpit making the ski slightly heavier, and stiffer.

Here's the thing - that first boat was one of the nicest boats ever in downwind conditions. The stiffer boat was still nice, but slightly less comfortable to handle.

So - for me, not being the most stable paddler in the world - the more flexible boat was nicer to use in downwind conditions. And for me, "nicer" translates as easier to handle and therefore, in this case, faster.

Confusing, huh?

Hi Rob,

It's always confusing even when its simple.

The weight of carbon is a benefit (or disadvantage to some) so should be included in the test. To me the test should be a carbon boat and a glass boat being paddled by similar speed paddlers. Have them both paddle in good runs that are well within the capabilities of both paddlers(we're not trying to test for how tippy it is, rather the speed implications of the two materials in the runs). Also have each swap boats.

What the test is trying to prove here is does the glass go as well as the carbon in runs (exclude the tipsiness factor but include the weight advantages). Or does the flex of the glass which creates a rocker when the boat is on a downward run + the momentum the extra weight affords it bring it up to the same level of performance one gets from the stiffness and lightness of the carbon boat.

There are some views that the glass may go better, but then would the elite paddlers not be paddling them? In any case, an interesting test.

Thoughts?

davesyd_1970 wrote:

There are some views that the glass may go better, but then would the elite paddlers not be paddling them?

Correct me if I'm wrong but almost every race report I've read recently has shown that only a portion of some races are downwind, and many have sections that are flat, so in the flat the carbons stiffness is a factor.

Having said that would a race that was entirely downwind, start to finish produce a better comparison between the difference between the two lay-ups?

I am hoping that the "Doctor" (Rottnest Island to Perth) race in January will be a big downwind this year

Under most circumstances I'd take a lighter ski partly because from experience I feel that lighter boats are quicker to accelerate, but also because of the mental factor. (I was chatting to an elite paddler a few days ago who admitted that he felt he lost races recently because his mind was playing, "you're on a heavier ski, the other guys are faster" games with him.)

But so much depends on conditions. A few years ago I was paddling lots of downwind runs with a buddy who had two skis - a carbon one and a heavy old glass one.

I was usually beating him by about a minute when he paddled his carbon boat. Then we had a particularly hectic run in massive seas and I t-boned his boat, damaging it so the next run he used his old heavy boat.

The run was in messy, confused seas. I battled, unable to put sequences together because as soon as I got going down a run, a sideways wave would knock me off it. Really frustrating. I looked out to sea, and there was John cruising past me. Afterwards, he reckoned that the weight of his boat had really helped, the momentum enabling him to bounce the sideways waves and keep going.

So yeah, under almost all circumstances I think I'd want the lightest ski possible - but I'm willing to concede that under some conditions the weight (and flexibility) of a glass boat might be helpful!

During yesterday's wind-shortened Race 3 of the Surfki Series, there was a particularly steep, short swell approaching the turn-can before turning downwind.

The nose of my c/f ski got swept sharply sideways about 4 or 5 times (5 lap race), as it crested the swell (the nose hanging in the air, and me and the rest fo the ski yet to crest the swell); the sheer force of wind (gale force?) caused the nose to 'break away' about 20 - 30 degrees to the left.

Tricky when taking a racing line around a turn-can, even trickier when you have Dawid and Tom and Sean ONE LAP AHEAD, and passing me in tight quarters on my downwind side.... I did NOT want my ski blown into Dawids lap!

Afterwards I commented to a few fellow paddlers that it was one of the few times I would have preffered a HEAVIER ski; the difference between a 12kg ski and a 16+kg one (say 25% heavier) just keep the ski better planted in high wind conditions.

Do you really think that the weight was the deciding factor in that situation?
I would imagine 'your weight', plus the area of the rudder may have been more important.

There's a lot of area in the front of a ski for the wind to act upon, do you really think that a couple of percent weight difference would be noticeable?

Did the ski feel to pivot around you or the rudder?